1. Field of the Invention
The present invention relates to a magnetic recording medium where data track patterns and servo patterns are formed on both one surface and another surface of a disk-shaped substrate by patterns with recording regions and non-recording regions, a recording/reproducing apparatus equipped with such magnetic recording medium, and a method of manufacturing such magnetic recording medium.
2. Description of the Related Art
As one example of this type of magnetic recording medium, Japanese Laid-Open Patent Publication No. 2006-31855 discloses a double-sided magnetic disk for perpendicular recording. This magnetic disk is a DTR medium (discrete track medium) and has data region patterns and servo region patterns formed on both a front surface and a rear surface thereof. On this magnetic disk, the servo region patterns are arranged in different orders in the circumferential direction on the front surface and the rear surface, and therefore different patterns are formed on the front surface and the rear surface. More specifically, on this magnetic disk, as one example, the servo region patterns are arranged in an anticlockwise order on the front surface and the servo region patterns are arranged in a clockwise order on the rear surface.
When manufacturing this magnetic disk, a stamper for the front surface and a stamper for the rear surface that will be used to manufacture the magnetic disk by imprinting are manufactured first. More specifically, by carrying out exposure/lithography on a resist layer applied onto a master, an exposure pattern for the data region patterns and servo region patterns is formed. Next, by carrying out developing or the like on the resist layer on which the exposure/lithography has been completed, a concave/convex pattern composed of a resist layer is formed on the master. After this, once the surface of the master on which the concave/convex pattern is formed has been made electrically conductive, electroforming is carried out to form a layer of nickel. Next, after the nickel layer has been separated from the master, a center portion and the outer edge portion thereof are removed by punching out. By doing so, the stamper for the front surface, for example, is completed. After this, in the same way as the method of manufacturing the stamper for the front surface, the stamper for the rear surface is manufactured.
Next, the concave/convex patterns of both stampers are transferred to the body being processed to manufacture a magnetic disk by imprint lithography. More specifically, first, a resist is applied onto the front surface and the rear surface of the processed body and baked to form the respective resist layers. Next, the processed body and both stampers are set in an imprinting apparatus and the concave/convex patterns of both stampers are pressed into both resist layers of the processed body. By doing so, the concave/convex patterns of the stampers are transferred to the resist layers to form concave/convex patterns in the front surface and the rear surface of the processed body. After this, on each surface, the magnetic layer at the bottom surfaces of the concaves is removed by ion milling using the concave/convex pattern as a mask. By doing so, concave/convex patterns are formed in the magnetic layers. Next, a layer of non-magnetic material is formed so as to cover both concave/convex patterns of the processed body and reverse sputtering is carried out on the non-magnetic material to expose the magnetic material (convexes) from the surface of the non-magnetic material. By doing so, the surface of the processed body is smoothed. After this, by forming a carbon protective layer and applying a lubricating rub so as to cover the front surface and the rear surface, the magnetic disk is completed.